TECHNICAL FIELD
[0001] The present invention relates to a pressure sensitive sensor unit including a pressure
sensitive sensor that detects the magnitude of an applied load.
BACKGROUND ART
[0003] A known pressure sensitive sensor includes an upper circuit board having a pair of
interdigitated comb-shaped electrodes and a lower circuit board having a disk-shaped
electrode facing the comb-shaped electrodes. In this pressure sensitive sensor, at
least one of the three electrodes described above is a pressure sensitive resistive
body (see, for example, Patent Document 1 (paragraphs [0002] to [0005] and Figs. 1(a)
to 1(c))). In addition, another known pressure sensitive sensor includes an upper
circuit board having a disk-shaped pressure sensitive resistive body and a lower circuit
board having a disk-shaped counter electrode facing the pressure sensitive resistive
body (see, for example, Patent Document 1 (paragraphs [0006] to [0008] and Figs. 2(a)
to 2(c))).
[0004] In the pressure sensitive sensors described above, when a load is applied from above
to the upper circuit board, the electrodes arranged below the portion to which the
load is applied come into direct contact with each other. Then, as the load increases
further, the contact area between the electrodes increases and the resistance value
decreases. The pressure sensitive sensors described above detect the magnitude of
the load by using such a change in resistance value.
CITATION LIST
PATENT DOCUMENT
SUMMARY OF THE INVENTION
PROBLEM TO BE SOLVED BY THE INVENTION
[0006] Known pressure sensitive sensors such as those described above have a problem that
the range of a load that can be detected may be narrow.
[0007] A problem to be solved by the invention is to provide a pressure sensitive sensor
unit capable of detecting a wide range of loads.
MEANS FOR SOLVING PROBLEM
[0008]
- [1] According to a first aspect of the invention, a pressure sensitive sensor unit
includes: a first pressure sensitive sensor whose output changes according to a magnitude
of an applied load; a second pressure sensitive sensor whose output changes according
to a magnitude of an applied load; a plate member arranged so as to include the first
and second pressure sensitive sensors in plan view; a first load transmitting member
interposed between the first pressure sensitive sensor and the plate member; and a
second load transmitting member interposed between the second pressure sensitive sensor
and the plate member. The first load transmitting member transmits a load belonging
to a first load range to the first pressure sensitive sensor. The second load transmitting
member transmits a load belonging to a second load range larger than the first load
to the second pressure sensitive sensor.
- [2] According to a second aspect of the invention, in the pressure sensitive sensor
unit according to the first aspect, the second load transmitting member may not transmit
a load belonging to the first load range to the second pressure sensitive sensor.
- [3] According to a third aspect of the invention, in the pressure sensitive sensor
unit according to the first or second aspect, a height of the first load transmitting
member may be higher than a height of the second load transmitting member, or the
second load transmitting member may be softer than the first load transmitting member.
- [4] According to a fourth aspect of the invention, in the pressure sensitive sensor
unit according to any one of the first to third aspects, the first pressure sensitive
sensor may include first and second electrodes electrically connected to each other
by application of a load, the second pressure sensitive sensor may include third and
fourth electrodes electrically connected to each other by application of a load, and
the pressure sensitive sensor unit may include a resistive body electrically connected
in series to the first or second electrode of the first pressure sensitive sensor.
- [5] According to a fifth aspect of the invention, in the pressure sensitive sensor
unit according to the fourth aspect, a resistance value of the resistive body may
be larger than a resistance value in an ON state of the second pressure sensitive
sensor.
- [6] According to a sixth aspect of the invention, in the pressure sensitive sensor
unit according to the fourth or fifth aspect, the pressure sensitive sensor unit may
include a plurality of the first pressure sensitive sensors. The pressure sensitive
sensor unit may include: a first electrode group including a plurality of the first
electrodes electrically connected to each other; and a second electrode group including
a plurality of the second electrodes electrically connected to each other. The resistive
body may be electrically connected in series to the first or second electrode group.
- [7] According to a seventh aspect of the invention, in the pressure sensitive sensor
unit according to any one of the fourth to sixth aspects, the pressure sensitive sensor
unit may include: a first base material; and a second base material facing the first
base material. The first electrode may be provided on the first base material, and
the second electrode may be provided on the first base material so as to face a first
connection body provided on the second base material so as to face the first electrode
or be provided on the second base material so as to face the first electrode.
- [8] According to an eighth aspect of the invention, in the pressure sensitive sensor
unit according to any one of aspects 4 to 6, the pressure sensitive sensor unit may
include: a first base material; and a second base material facing the first base material.
The third electrode may be provided on the first base material, and the fourth electrode
may be provided on the first base material so as to face a second connection body
provided on the second base material so as to face the third electrode or be provided
on the second base material so as to face the third electrode.
- [9] According to a ninth aspect of the invention, in the pressure sensitive sensor
unit according to the seventh or eighth aspect, a height of the first load transmitting
member may be higher than a height of the second load transmitting member, the first
load transmitting member may be bonded to one of the first and second base materials
and bonded to the plate member, and the second load transmitting member may be bonded
to only one of the first base material, the second base material, and the plate member.
- [10] According to a tenth aspect of the invention, in the pressure sensitive sensor
unit according to any one of the seventh to ninth aspects, the pressure sensitive
sensor unit may include a spacer interposed between the first base material and the
second base material. The spacer may include: a first opening in which the first and
second electrodes of the first pressure sensitive sensor are housed; and a second
opening in which the third and fourth electrodes of the second pressure sensitive
sensor are housed. A width of the first opening may be larger than a width of the
second opening.
- [11] According to an eleventh aspect of the invention, in the pressure sensitive sensor
unit according to any one of the first to tenth aspects, the pressure sensitive sensor
unit may include: a plurality of the first pressure sensitive sensors; and a plurality
of the first load transmitting members. The plurality of first pressure sensitive
sensors may be arranged around the second pressure sensitive sensor, and the plurality
of first load transmitting members may be arranged around the second load transmitting
member.
EFFECT OF THE INVENTION
[0009] The pressure sensitive sensor unit according to the invention includes the first
load transmitting member that transmits a load belonging to the first load range to
the first pressure sensitive sensor and the second load transmitting member that transmits
a load belonging to the second load range larger than the first load range to the
second pressure sensitive sensor. Therefore, since the pressure sensitive sensor unit
according to the invention can detect a load in both the first range and the second
range, it is possible to increase the detectable load range.
BRIEF DESCRIPTION OF DRAWINGS
[0010]
Fig. 1 is a plan view showing an example of a pressure sensitive sensor unit according
to an embodiment of the invention;
Fig. 2 is a cross-sectional view taken along the line II-II of Fig. 1;
Fig. 3(a) is a cross-sectional view showing a state in which a low load is applied
to the pressure sensitive sensor unit in Fig. 2, and Fig. 3(b) is a cross-sectional
view showing a state in which a high load is applied to the pressure sensitive sensor
unit in Fig. 2;
Fig. 4 is a graph showing the relationship between the magnitude F of a load applied
to the pressure sensitive sensor unit according to the embodiment of the invention
and a resistance value R output from the pressure sensitive sensor unit;
Fig. 5 is a cross-sectional view showing a first modification example of the pressure
sensitive sensor unit according to the embodiment of the invention;
Fig. 6 is a cross-sectional view showing a second modification example of the pressure
sensitive sensor unit according to the embodiment of the invention;
Fig. 7(a) is an enlarged plan view showing a pressure sensitive sensor according to
a third modification example of the pressure sensitive sensor unit according to the
embodiment of the invention, Fig. 7(b) is an enlarged plan view showing a lower membrane
of the pressure sensitive sensor unit in Fig. 7(a), and Fig. 7(c) is an enlarged plan
view showing a spacer and an upper membrane of the pressure sensitive sensor unit
in Fig. 7(a); and
Fig. 8 is an enlarged plan view showing a pressure sensitive sensor according to a
fourth modification example of the pressure sensitive sensor unit according to the
embodiment of the invention, Fig. 8(b) is an enlarged plan view showing a lower membrane
of the pressure sensitive sensor in Fig. 8(a), and Fig. 8(c) is an enlarged plan view
showing an upper membrane of the pressure sensitive sensor in Fig. 8(a).
MODE(S) FOR CARRYING OUT THE INVENTION
[0011] Hereinafter, an embodiment of the invention will be described with reference to the
diagrams.
[0012] Fig. 1 is a plan view showing an example of a pressure sensitive sensor unit according
to an embodiment of the invention. Fig. 2 is a cross-sectional view taken along the
line II-II of Fig. 1. In addition, Fig. 2 shows a pressure sensitive sensor unit in
an unloaded state in which no load is applied.
[0013] A pressure sensitive sensor unit 1A is a pressure sensitive sensor unit whose output
changes according to the magnitude of the applied load. In the present embodiment,
a resistance value is used as this output. In addition, this output is not limited
to the resistance value, but may be, for example, a voltage value.
[0014] As shown in Figs. 1 and 2, the pressure sensitive sensor unit 1A according to the
present embodiment includes a pressure sensitive sensor sheet 2, a plurality of (four
in this example) first load transmitting members 3A to 3D, a second load transmitting
member 4, and a plate member 5.
[0015] The pressure sensitive sensor sheet 2 includes pressure sensitive sensors 2A to 2E
whose resistance values change according to the magnitude of the applied load. In
the present embodiment, the first pressure sensitive sensors 2A to 2D are used to
detect a load (low load) belonging to a first load range (low load range), and the
second pressure sensitive sensor 2E is used to detect a load (high load) belonging
to a second load range (high load range) larger than the first load range.
[0016] Here, the load range refers to a range of the magnitude of the load. The first load
range is not particularly limited, but may be, for example, 20 gf to 500 gf, and the
second load range is not particularly limited, but may be, for example, 500 gf to
2000 gf.
[0017] As shown in Figs. 1 and 2, the pressure sensitive sensor sheet 2 according to the
present embodiment includes a lower membrane substrate 10, an upper membrane substrate
20, and a spacer 30.
[0018] As shown in Figs. 1 and 2, the lower membrane substrate 10 has a first base material
11, a first wiring pattern 12, a first electrode group 13 (13A to 13D), a second electrode
group 14 (14A to 14D), a third electrode 13E, a fourth electrode 14E, a second wiring
pattern 15, a resistive body 16, and a third wiring pattern 17.
[0019] The first base material 11 of the lower membrane substrate 10 is a film-like member
formed of a flexible and electrically insulating material. Examples of the material
that makes up the first base material 11 include resin materials. More specifically,
polyethylene terephthalate (PET) or polyethylene naphthalate (PEN) can be exemplified.
In addition, the first base material 11 does not have to be flexible.
[0020] As shown in Fig. 1, the first wiring pattern 12 is formed on the upper surface of
the first base material 11. The first wiring pattern 12 in the present embodiment
functions as a lead-out wiring that electrically connects the above-described first
electrode group 13 and third electrode 13E to a power supply (not shown).
[0021] The first wiring pattern 12 has a first wiring portion 121a, a second wiring portion
121b, and a first external terminal portion 122. The first wiring portion 121a has
a U-shaped linear shape. One end of the first wiring portion 121a is connected to
the second wiring portion 121b. The second wiring portion 121b has an L-shaped linear
shape, and one end of the second wiring portion 121b is connected to the first external
terminal portion 122. The first external terminal portion 122 is a terminal portion
that is electrically connected to a power supply (not shown).
[0022] The first wiring pattern 12 is formed by printing a conductive paste on the upper
surface of the first base material 11 and solidifying (curing) the conductive paste.
The conductive paste is made by mixing conductive particles and a binder resin with
water or a solvent and various additives. The conductive paste that makes up the first
wiring pattern 12 is a low-resistance conductive paste having a relatively small electrical
resistance value. In addition, the method of forming the first wiring pattern 12 is
not particularly limited to the above. For example, instead of using the conductive
paste, the first wiring pattern 12 may be formed by etching a metal foil.
[0023] Specific examples of conductive particles include silver, copper, nickel, tin, bismuth,
zinc, indium, palladium, and alloys thereof. In addition, specific examples of the
binder resin include acrylic resin, polyester resin, epoxy resin, vinyl resin, urethane
resin, phenol resin, polyimide resin, silicone resin, and fluorine resin. In addition,
examples of the solvent contained in the conductive paste include α-terpineol, butyl
carbitol acetate, butyl carbitol, 1-decanol, butyl cellosolve, diethylene glycol monoethyl
ether acetate, and tetradecane.
[0024] Although not particularly limited, in the present embodiment, a silver paste containing
silver as a main component of conductive particles or a copper paste containing copper
as a main component of conductive particles is used as the low-resistance conductive
paste. In addition, metal salts may be used as conductive particles contained in the
conductive paste. As metal salts, salts of the metals described above can be mentioned.
In addition, the binder resin may be omitted from the conductive paste described above.
In addition, instead of the conductive paste described above, a conductive ink may
be used.
[0025] The method of applying the conductive paste is not particularly limited, but either
a contact application method or a non-contact application method may be used. Specific
examples of the contact application method include screen printing, gravure printing,
offset printing, gravure offset printing, and flexographic printing. On the other
hand, specific examples of the non-contact application method include inkjet printing,
a spray coating method, a dispense coating method, and a jet dispensing method. In
addition, the heat source for curing the conductive paste is not particularly limited,
but examples thereof include an electric heating oven, an infrared oven, a far-infrared
oven (IR), a near-infrared oven (NIR), and a laser irradiation device, and a heat
treatment using a combination thereof may also be applied.
[0026] The first electrode group 13 is connected to the first wiring portion 121a of the
first wiring pattern 12. The first electrode group 13 includes a plurality of (four
in this example) first electrodes 13A to 13D. In the first electrode group 13, the
first electrodes 13A to 13D are arranged on the first wiring portion 121a so as to
be electrically connected in parallel to each other. In addition, in the present embodiment,
the first electrodes 13A to 13D are arranged so as to surround the third electrode
13E and the fourth electrode 14E.
[0027] In the present embodiment, the first electrodes 13A to 13D all have the same configuration.
Therefore, the configuration of the first electrode 13A will be described herein as
a representative example.
[0028] The first electrode 13A is a comb-shaped electrode. The first electrode 13A has a
connection wiring portion 131 and a plurality of (three in this example) comb-tooth
portions 132. The connection wiring portion 131 is a linear portion extending along
the Y direction in the diagram, and one end of the connection wiring portion 131 is
connected to the first wiring portion 121a of the first wiring pattern 12.
[0029] The plurality of comb-tooth portions 132 are connected to the other end side of the
connection wiring portion 131. As shown in Figs. 1 and 2, the plurality of comb-tooth
portions 132 are aligned in parallel along the Y direction in the diagrams, and protrude
from the connection wiring portion 131 in the +X direction in the diagrams.
[0030] The second electrode group 14 is arranged on the first base material 11 so as to
be adjacent to the first electrode group 13. The second electrode group 14 includes
a plurality of (four in this example) second electrodes 14A to 14D.
[0031] The second electrodes 14A to 14D are arranged adjacent to the first electrodes 13A
to 13D, respectively. In addition, the second electrodes 14A to 14D are arranged slightly
spaced apart from the first electrodes 13A to 13D so as to be electrically insulated
from the first electrodes 13A to 13D. In the present embodiment, the second electrodes
14A to 14D are arranged so as to surround the third electrode 13E and the fourth electrode
14E, similarly to the first electrodes 13A to 13D.
[0032] In addition, in the present embodiment, the plurality of first pressure sensitive
sensors 2A to 2D are arranged so as to surround the second pressure sensitive sensor
2E, but the invention is not limited to this. For example, in the pressure sensitive
sensor unit 1A, the first pressure sensitive sensor and the second pressure sensitive
sensor may be arranged alternately.
[0033] In the present embodiment, the second electrodes 14A to 14D all have the same configuration.
Therefore, the configuration of the second electrode 14A will be described herein
as a representative example.
[0034] The second electrode 14A has a planar shape point-symmetrical with respect to the
first electrode 13A. The second electrode 14A has a connection wiring portion 141
and a plurality of (three in this example) comb-tooth portions 142. The connection
wiring portion 141 is a linear portion extending along the Y direction in the diagram.
The plurality of comb-tooth portions 142 are connected to one end side of the connection
wiring portion 141. The plurality of comb-tooth portions 142 are aligned along the
Y direction in the diagram, and protrude from the connection wiring portion 141 in
the -X direction in the diagram. Then, the comb-tooth portions 142 are inserted between
the comb-tooth portions 132 of the first electrode 13A, and face the comb-tooth portions
132 of the first electrode 13A along the Y direction in the diagram.
[0035] The above-described first and second electrodes 13A to 13D and 14A to 14D are formed
by printing a conductive paste on the upper surface of the first base material 11
and then solidifying (curing) the conductive paste. The conductive paste is a high-resistance
conductive paste having a relatively high electrical resistance. In addition, instead
of the conductive paste, a conductive ink may be used.
[0036] Examples of conductive particles contained in the conductive paste include carbon.
Specific examples of the carbon include graphite and carbon black. In addition, specific
examples of the binder resin and the solvent include the materials described above.
In addition, the binder resin may be omitted from the conductive paste. The method
of applying the conductive paste is not particularly limited, but either the contact
application method or the non-contact application method described above may be used.
[0037] The second wiring pattern 15 is connected to the other ends of the connection wiring
portions 141 of the second electrodes 14A to 14D. The second wiring pattern 15 electrically
connects the second electrodes 14A to 14D and the resistive body 16 to each other.
[0038] The second wiring pattern 15 is formed of the same material as the first wiring pattern
12 although there is no particular limitation thereto. In addition, although not particularly
limited, the second wiring pattern 15 is formed by printing a conductive paste on
the upper surface of the first base material 11 and solidifying (curing) the conductive
paste, similarly to the first wiring pattern 12.
[0039] The second wiring pattern 15 has a third wiring portion 151 and a first resistive
body connection portion 153. The third wiring portion 151 has a linear shape, and
the second electrodes 14A to 14D are arranged on the third wiring portion 151 so as
to be electrically connected in parallel to each other.
[0040] The first resistive body connection portion 153 is connected to the other end of
the third wiring portion 151. The first resistive body connection portion 153 in the
present embodiment is a land pattern that is wider than the third wiring portion 151,
although there is no particular limitation thereto.
[0041] The resistive body 16 is connected to the first resistive body connection portion
153. The resistive body 16 in the present embodiment is arranged on the second wiring
pattern 15 so as to be electrically connected in series to the second electrode group
14. The resistive body 16 has a resistance value R
1 (constant) larger than the resistance value R
x2 in the ON state of the second pressure sensitive sensor 2E. The resistive body 16
is provided to make the combined resistance R
0 (= R
1 + R
x1) of the resistance value R
1 of the resistive body 16 and the resistance value R
x1 in the ON state of the first pressure sensitive sensors 2A to 2D larger than the
resistance value R
x2 in the ON state of the second pressure sensitive sensor 2E (R
0 > R
x2).
[0042] In addition, the "ON state" of the first pressure sensitive sensors 2A to 2D is a
state in which the first electrodes 13A to 13D and the second electrodes 14A to 14D
are electrically connected to each other through connection bodies 22A to 22D, and
the "ON state" of the second pressure sensitive sensor 2E is a state in which the
third electrode 13E and the fourth electrode 14E are electrically connected to each
other through a connection body 22E. Here, in the present embodiment, "electrically
connecting" a connection body and an electrode means a state in which the resistance
value between the connection body and the electrode is equal to or less than a predetermined
threshold value, and does not include a state in which the connection body and the
electrode are simply in contact with each other. In addition, the resistance values
R
x1 and R
x2 in the "ON state" are variables that change according to the magnitude of the load,
as will be described later.
[0043] The resistive body 16 may be a resistor although there is no particular limitation
thereto. Alternatively, the resistive body 16 may be formed by printing a high-resistance
conductive paste on the upper surface of the first base material 11 and solidifying
(curing) the conductive paste. Examples of conductive particles contained in the conductive
paste include the above-described carbon. In addition, specific examples of the binder
resin and the solvent include the materials described above. In addition, the binder
resin may be omitted from the conductive paste. The method of applying the conductive
paste is not particularly limited, but either the contact application method or the
non-contact application method described above may be used.
[0044] In the present embodiment, the resistive body 16 is electrically connected in series
to the second electrode group 14 and is arranged on the power supply side with respect
to the first pressure sensitive sensors 2A to 2D, but is not limited thereto. For
example, the resistive body 16 may be electrically connected in series to the first
electrode group 13 and arranged on the power supply side with respect to the first
pressure sensitive sensors 2A to 2D.
[0045] Although not particularly shown, specifically, in the first wiring pattern 12 shown
in Fig. 1, by interposing the resistive body 16 between the first wiring portion 121a
and the second wiring portion 121b, the resistive body 16 can be electrically connected
in series to all of the first electrodes 13A and 13B included in the first electrode
group 13. In this case as well, the above-described combined resistance R
0 (= R
1 + R
x1) can be made larger than the resistance value R
x2 in the ON state of the second pressure sensitive sensor 2E (R
0 > R
x2).
[0046] The comb-shaped third electrode 13E is connected to the other end of the second wiring
portion 121b of the first wiring pattern 12. The third electrode 13E has the same
configuration as the first electrode 13A, and includes a connection wiring portion
131 and a plurality of comb-tooth portions 132. However, the connection wiring portion
131 of the third electrode 13E extends along the X direction in the diagram. In addition,
the comb-tooth portions 132 are aligned along the X direction in the diagram, and
protrude from the connection wiring portion 131 in the -Y direction in the diagram.
[0047] The comb-shaped fourth electrode 14E is arranged on the first base material 11 so
as to be adjacent to the third electrode 13E. The fourth electrode 14E is arranged
slightly spaced apart from the third electrode 13E so as to be electrically insulated
from the third electrode 13E.
[0048] The fourth electrode 14E has the same configuration as the second electrode 14A,
and includes a connection wiring portion 141 and a plurality of comb-tooth portions
142. However, the connection wiring portion 141 of the fourth electrode 14E extends
along the X direction in the diagram. In addition, the comb-tooth portions 142 of
the fourth electrode 14E are aligned along the X direction in the diagram, and protrude
from the connection wiring portion 141 in the +Y direction in the diagram.
[0049] The third wiring pattern 17 is connected to the resistive body 16 and the fourth
electrode 14E. The third wiring pattern 17 functions as a lead-out wiring that electrically
connects the second electrode group 14 and the fourth electrode 14E to the ground
(not shown).
[0050] The third wiring pattern 17 has a fourth wiring portion 171a, a fifth wiring portion
171b, a second external terminal portion 172, and a second resistive body connection
portion 173. The fourth wiring portion 171a has a linear shape extending in the Y
direction in the diagram, and one end of the fourth wiring portion 171a is connected
to the second external terminal portion 172.
[0051] The second external terminal portion 172 is a terminal portion that is electrically
connected to the ground (not shown). In addition, in the present embodiment, the first
external terminal portion 122 of the first wiring pattern 12 is electrically connected
to a power supply (not shown) and the second external terminal portion 172 of the
third wiring pattern 17 is connected to the ground (not shown), but the invention
is not limited thereto. Contrary to the present embodiment, the first external terminal
portion 122 may be electrically connected to the ground (not shown), and the second
external terminal portion 172 may be connected to the power supply (not shown).
[0052] The other end of the fourth wiring portion 171a is connected to the second resistive
body connection portion 173. The second resistive body connection portion 173 is a
land pattern that is wider than the fourth wiring portion 171a, although there is
no particular limitation thereto. The resistive body 16 is connected to the second
resistive body connection portion 173, and the fourth wiring portion 171a is electrically
connected to the second electrode group 14 through the resistive body 16 and the third
wiring pattern 17. As a result, the second electrode group 14 is electrically connected
to the ground (not shown).
[0053] The fifth wiring portion 171b has a linear shape extending in the X direction in
the diagram, and one end of the fifth wiring portion 171b is connected to the fourth
wiring portion 171a. On the other hand, the other end of the fifth wiring portion
171b is connected to the fourth electrode 14E. Therefore, the fourth electrode 4E
is electrically connected to the ground (not shown) through the third wiring pattern
17.
[0054] The resistance value output from the pressure sensitive sensor unit 1A according
to the present embodiment is a resistance value between the first external terminal
portion 122 and the second external terminal portion 172 although there is no particular
limitation thereto. The resistance value can be obtained by using, for example, a
resistance measuring device such as a tester connected to the first external terminal
portion 122 and the second external terminal portion 172.
[0055] As shown in Figs. 1 and 2, the upper membrane substrate 20 is arranged above the
lower membrane substrate 10. The upper membrane substrate 20 has a second base material
21 and a plurality of (five in this example) connection bodies 22A to 22E.
[0056] The second base material 21 of the upper membrane substrate 20 is a film-like member
formed of a flexible and electrically insulating material. Examples of the material
that makes up the second base material 21 include resin materials. More specifically,
polyethylene terephthalate (PET) or polyethylene naphthalate (PEN) can be exemplified.
In addition, a metal film may be used as the second base material 21. In this case,
the second base material 21 may have the functions of the connection bodies 22A to
22E, that is, the second base material 21 may also serve as the connection bodies
22A to 22E.
[0057] As shown in Figs. 1 and 2, the disk-shaped connection bodies 22A to 22E are formed
on the lower surface of the second base material 21. The connection bodies 22A to
22D are members that come into contact with the first electrodes 13A to 13D and the
second electrodes 14A to 14D to electrically connect the first electrodes 13A to 13D
and the second electrodes 14A to 14D to each other. That is, the connection body 22A
comes into contact with the first electrode 13A and the second electrode 14A to electrically
connect the first electrode 13A and the second electrode 14A to each other. The connection
body 22B comes into contact with the first electrode 13B and the second electrode
14B to electrically connect the first electrode 13B and the second electrode 14B to
each other. The connection body 22C comes into contact with the first electrode 13C
and the second electrode 14C to electrically connect the first electrode 13C and the
second electrode 14C to each other. The connection body 22D comes into contact with
the first electrode 13D and the second electrode 14D to electrically connect the first
electrode 13D and the second electrode 14D to each other. In addition, the connection
body 22E is also a member that comes into contact with the third electrode 13E and
the fourth electrode 14E to electrically connect the third electrode 13E and the fourth
electrode 14E to each other.
[0058] All of the connection bodies 22A to 22E are arranged so as to face parts of the connection
wiring portions 131 and 141 and the comb-tooth portions 132 and 142, and have a size
to include almost the entire comb-tooth portions 132 and 142 thereinside in plan view.
[0059] The connection bodies 22A to 22E are formed by printing a low-resistance conductive
paste on the lower surface of the second base material 21 and curing the low-resistance
conductive paste, similarly to the first wiring pattern 12 described above. That is,
the connection bodies 22A to 22E are formed of a material having a lower electrical
resistivity than the material that makes up the first to fourth electrodes 13A to
13E and 14A to 14E.
[0060] In addition, the connection bodies 22A to 22E may have a protective layer covering
the above-described layer that is formed by printing and curing a high-resistance
conductive paste. This protective layer is formed by printing and curing the above-described
high-resistance conductive paste.
[0061] The spacer 30 is a film-like member formed of a flexible and electrically insulating
material, similar to the first and second base materials 11 and 21 described above.
Examples of the material that makes up the spacer 30 include resin materials. More
specifically, polyethylene terephthalate (PET) or polyethylene naphthalate (PEN) can
be exemplified. Alternatively, a double-sided adhesive tape can be exemplified as
the spacer 30. A double-sided adhesive tape having adhesive layers formed on both
surfaces of a base material may be used, or a double-sided adhesive tape having only
adhesive layers may be used.
[0062] As shown in Figs. 1 and 2, the spacer 30 is interposed between the first base material
11 and the second base material 21, and the lower membrane substrate 10 and the upper
membrane substrate 20 are stacked with the spacer 30 interposed therebetween. Specifically,
the upper surface of the base material 11 of the lower membrane substrate 10 and the
lower surface of the spacer 30 are attached to each other through an adhesive layer
(not shown), and the upper surface of the spacer 30 and the lower surface of the base
material 21 of the upper membrane substrate 20 are attached to each other through
an adhesive layer (not shown).
[0063] The spacer 30 has a plurality of (four in this example) first openings 31 and a second
opening 32. The plurality of first openings 31 are arranged so as to surround the
second opening 32, as shown in Fig. 1. In addition, when the first pressure sensitive
sensor and the second pressure sensitive sensor are arranged alternately as described
above, the first opening and the second opening are also arranged alternately.
[0064] Each of the first openings 31 has a circular planar shape. Parts of the connection
wiring portions 131 of the first electrodes 13A to 13D, the comb-tooth portions 132
of the first electrodes 13A to 13D, parts of the connection wiring portions 141 of
the second electrodes 14A to 14D, and the comb-tooth portions 142 of the second electrodes
14A to 14D are housed in the first openings 31. In addition, the connection bodies
22A to 22D of the upper membrane substrate 20 are also housed in the first openings
31. In addition, the diameters of the connection bodies 22A to 22D may be larger than
the inner diameter of the first opening 31.
[0065] When the membrane substrates 10 and 20 are stacked with the spacer 30 interposed
therebetween, the connection bodies 22A to 22D and the comb-tooth portions 132 and
142 of the first and second electrodes 13A to 13D and 14A to 14D face each other with
the first opening 31 interposed therebetween. In addition, similarly, the connection
bodies 22A to 22D and parts of the connection wiring portions 131 and 141 of the first
and second electrodes 13A to 13D and 14A to 14D face each other.
[0066] The second opening 32 also has a circular planar shape, and parts of the connection
wiring portions 131 and 141 of the third and fourth electrodes 13E and 14E and the
comb-tooth portions 132 and 142 of the third and fourth electrodes 13E and 14E are
housed in the second opening 32. In addition, the connection body 22E of the upper
membrane substrate 20 is also housed in the second opening 32. In addition, the diameter
of the connection body 22E may be larger than the inner diameter of the second opening
32.
[0067] In addition, when the membrane substrates 10 and 20 are stacked with the spacer 30
interposed therebetween, the connection body 22E and the comb-tooth portions 132 and
142 of the third and fourth electrodes 13E and 14E face each other with the second
opening 32 interposed therebetween. In addition, similarly, the connection body 22E
and parts of the connection wiring portions 131 and 141 of the third and fourth electrodes
13E and 14E face each other.
[0068] As shown in Figs. 1 and 2, the spacer 30 ensures a distance between the connection
bodies 22A to 22D and the comb-tooth portions 132 and 142 of the first and second
electrodes 13A to 13D and 14A to 14D. In addition, the spacer 30 ensures a distance
between the connection body 22E and the comb-tooth portions 132 and 142 of the third
and fourth electrodes 13E and 14E.
[0069] Here, the second opening 32 in the present embodiment has the same width as the first
opening 31. That is, as shown in Fig. 2, the diameter D
2 of the second opening 32 is the same as the diameter D
1 of the first opening 31 (D
1 = D
2).
[0070] In addition, although the diameter D
1 of the first opening 31 and the diameter D
2 of the second opening 32 are the same length in the present embodiment, the invention
is not limited thereto. The diameter D
1 of the first opening 31 may be larger than the diameter D
2 of the second opening 32 (D
1 > D
2). Thus, the width of the first opening 31 is larger than the width of the second
opening 32, so that the second base material 21 is likely to bend at the first opening
31. Therefore, since the magnitude of the on-load of the first pressure sensitive
sensors 2A to 2D can be reduced, it is possible to improve the sensitivity of the
first pressure sensitive sensors 2A to 2D in the low load range. In addition, the
"on-load" is a load required to switch the pressure sensitive sensor from the OFF
state to the ON state.
[0071] In addition, the planar shape of each of the first and second openings 31 and 32
is not limited to a circle, but may be, for example, an ellipse, an oval, a rectangle,
or a polygon. In addition, the shapes of the connection bodies 22A to 22E or the electrodes
13A to 13E and 14A to 14E are not particularly limited to those described above, and
may be, for example, shapes corresponding to the shapes of the first and second openings
31 and 32.
[0072] In addition, in the present embodiment, the thickness of the spacer 30 is set so
that the connection bodies 22A to 22E are not in contact with the comb-tooth portions
132 and 142 when no load is applied, but the invention is not particularly limited
thereto. The thickness of the spacer 30 may be set so that the connection bodies 22A
to 22E are always in contact with the comb-tooth portions 132 and 142. Similarly,
the thickness of the spacer 30 may be set so that the connection bodies 22A to 22E
are always in contact with the connection wiring portions 131 and 141.
[0073] In addition, in the present embodiment, all of the first pressure sensitive sensors
2A to 2D and the second pressure sensitive sensor 2E are formed by the membrane substrates
10 and 20 and the spacer 30 of the pressure sensitive sensor sheet 2. However, the
invention is not limited thereto, and the first and second pressure sensitive sensors
2A to 2E may be formed by separate membrane substrates and spacers. That is, the pressure
sensitive sensor unit may be a unit formed by a plurality of pressure sensitive sensor
sheets.
[0074] In addition, in this case, since the electrodes formed on the base material are likely
to bend by reducing the thickness of the spacer of the pressure sensitive sensor sheet
in which the first pressure sensitive sensor for low load is formed, it is possible
to improve the sensitivity of the sensor in the low load range. Alternatively, since
the electrodes are likely to bend by reducing the thickness of the base material,
it is possible to improve the sensitivity of the sensor in the low load range.
[0075] In the pressure sensitive sensor sheet 2 according to the present embodiment, the
connection bodies 22A to 22D and the first and second electrodes 13A to 13D and 14A
to 14D form the first pressure sensitive sensors 2A to 2D and function as first detection
units 135A to 135D that detect a load applied to the first pressure sensitive sensors
2A to 2D. That is, the connection body 22A, the first electrode 13A, and the second
electrode 14A form the first pressure sensitive sensor 2A and function as the first
detection unit 135A that detects a load applied to the first pressure sensitive sensor
2A. The connection body 22B, the first electrode 13B, and the second electrode 14B
form the first pressure sensitive sensor 2B and function as the first detection unit
135B that detects a load applied to the first pressure sensitive sensor 2B. The connection
body 22C, the first electrode 13C, and the second electrode 14C form the first pressure
sensitive sensor 2C and function as the first detection unit 135C that detects a load
applied to the first pressure sensitive sensor 2C. The connection body 22D, the first
electrode 13D, and the second electrode 14D form the first pressure sensitive sensor
2D and function as the first detection unit 135D that detects a load applied to the
first pressure sensitive sensor 2D. On the other hand, the connection body 22E and
the third and fourth electrodes 13E and 14E form the second pressure sensitive sensor
2E and function as a second detection unit 135E that detects a load applied to the
second pressure sensitive sensor 2E.
[0076] Specifically, when a load is applied to the first detection units 135A to 135D of
the first pressure sensitive sensor 2A to 2D, the second base material 21 bends downward
at the first opening 31, and the connection bodies 22A to 22D come into contact with
the first and second electrodes 13A to 13D and 14A to 14D. Here, as the magnitude
of the load applied to the first detection units 135A to 135D increases, the contact
area between the connection bodies 22A to 22D and the first and second electrodes
13A to 13D and 14A to 14D increases. Therefore, the resistance value R
x1 between the first and second electrodes 13A to 13D and 14A to 14D decreases. That
is, in the first pressure sensitive sensors 2A to 2D, as the magnitude of the applied
load increases, the resistance value R
x1 that is output decreases.
[0077] Similarly, even when a load is applied to the second detection unit 135E of the second
pressure sensitive sensor 2E, the second base material 21 bends downward at the second
opening 32, and the connection body 22E comes into contact with the third and fourth
electrodes 13E and 14E. In this case as well, as the magnitude of the load applied
to the second detection unit 135E increases, the contact area between the connection
body 22E and the third and fourth electrodes 13E and 14E increases. Therefore, the
resistance value R
x2 between the third and fourth electrodes 13E and 14E decreases. That is, in the second
pressure sensitive sensor 2E as well, as the magnitude of the applied load increases,
the resistance value R
x2 that is output decreases.
[0078] In the present embodiment, the first electrodes 13A to 13D and the third electrode
13E have the same configuration, and the second electrodes 14A to 14D and the fourth
electrode 14E have the same configuration. Therefore, the resistance value R
x1 in the ON state of the first pressure sensitive sensors 2A to 2D is approximately
the same as the resistance value R
x2 in the ON state of the second pressure sensitive sensor 2E (R
x1 = R
x2).
[0079] In addition, in the present embodiment, the first pressure sensitive sensors 2A to
2D are electrically connected in parallel to each other between the first wiring pattern
12 and the second wiring pattern 15. Then, the first pressure sensitive sensor 2E
is electrically connected in parallel with the first pressure sensitive sensors 2A
to 2D between the first wiring pattern 12 and the second wiring pattern 15.
[0080] A plurality of (four in this example) first load transmitting members 3A to 3D and
a second load transmitting member 4 are provided on the upper surface of the second
base material 21 of the pressure sensitive sensor sheet 2. The first load transmitting
members 3A to 3D are members (actuators) for transmitting a load to the first pressure
sensitive sensors 2A to 2D. On the other hand, the second load transmitting member
4 is a member (actuator) for transmitting a load to the second pressure sensitive
sensor 2E.
[0081] In the present embodiment, the first load transmitting members 3A to 3D and the second
load transmitting member 4 are members each having a circular planar shape and having
elasticity. That is, the first load transmitting members 3A to 3D and the second load
transmitting member 4 are members that contract when a load is applied but return
to their initial shapes before the load is applied when the load is removed. In addition,
the planar shapes of the first load transmitting members 3A to 3D and the second load
transmitting member 4 are not limited to the circular shape. The planar shape is not
limited to a circle, and may be, for example, an ellipse, an oval, a rectangle, or
a polygon. In addition, the first load transmitting members 3A to 3D and the second
load transmitting member 4 may be rigid bodies.
[0082] Specific examples of the member having elasticity as described above include a resin
member, a rubber member, and a spring member. Among these, it is particularly preferable
to use a sponge-like resin member containing fine bubbles.
[0083] As shown in Fig. 2, the first load transmitting members 3A to 3D are interposed between
the first detection units 135A to 135D of the first pressure sensitive sensors 2A
to 2D and the plate member 5. Specifically, the lower surfaces of the first load transmitting
members 3A to 3D are attached to the upper surface of the second base material 21
of the upper membrane substrate 20 through an adhesive layer (not shown), and the
upper surfaces of the first load transmitting members 3A to 3D are attached to the
lower surface of the plate member 5 through an adhesive layer (not shown). That is,
both the upper and lower surfaces of the first load transmitting members 3A to 3D
are fixed to the second base material 21 and the plate member 5.
[0084] In addition, the first load transmitting members 3A to 3D are bonded to the second
base material 21 and the plate member 5 through an adhesive layer, but the invention
is not limited thereto. For example, the first load transmitting members 3A to 3D
may be bonded to the second base material 21 or the plate member 5 by being applied
and formed thereon.
[0085] The second load transmitting member 4 is interposed between the second detection
unit 135E of the second pressure sensitive sensor 2E and the plate member 5. The lower
surface of the second load transmitting member 4 is attached to the upper surface
of the second base material 21 of the upper membrane substrate 20 through an adhesive
layer (not shown), but the upper surface of the second load transmitting member 4
is spaced apart from the plate member 5. That is, only the lower surface of the second
load transmitting member 4 is fixed to the second base material 21.
[0086] In addition, the second load transmitting member 4 is bonded to the second base material
21 through an adhesive layer, but the invention is not limited thereto. For example,
the second load transmitting member 4 may be bonded to the second base material 21
by being applied and formed thereon. In addition, the lower surface of the second
load transmitting member 4 is fixed to the second base material 21, but the invention
is not limited thereto. The upper surface of the second load transmitting member 4
may be bonded to the plate member 5, and the lower surface of the second load transmitting
member 4 may be spaced apart from the second base material 21.
[0087] The height T
1 of the first load transmitting members 3A to 3D is higher than the height T
2 of the second load transmitting member 4 (T
1 > T
2). In this manner, by making a difference between the height T
1 of the first load transmitting members 3A to 3D and the height T
2 of the second load transmitting member 4, the load can be transmitted to the first
pressure sensitive sensors 2A to 2D before the second pressure sensitive sensor 2E.
That is, when a low load is applied to the pressure sensitive sensor unit 1A, the
load is transmitted to the first pressure sensitive sensors 2A to 2D by the first
load transmitting members 3A to 3D, but the load is not transmitted to the second
pressure sensitive sensor 2E by the second load transmitting member 4. On the other
hand, when a high load is applied to the pressure sensitive sensor unit 1A, the load
is also transmitted to the second pressure sensitive sensor 2E by the second load
transmitting member 4.
[0088] The plate member 5 overlaps the pressure sensitive sensor sheet 2 with the first
and second load transmitting members 3A to 3D interposed therebetween, and is arranged
so as to include the first and second pressure sensitive sensors 2A to 2E in plan
view. The plate member 5 is a plate-shaped member formed of a material having a predetermined
rigidity. By forming the plate member 5 with a member that is difficult to bend, it
is possible to generate a uniform pressing force on the lower surface of the plate
member 5. Examples of the material that makes up the plate member 5 include an ABS
(acrylonitrile butadiene styrene) resin, glass, and a polycarbonate resin.
[0089] The load transmission by the first load transmitting members 3A to 3D and the second
load transmitting member 4 will be specifically described with reference to Figs.
3(a) and 3(b). Fig. 3(a) is a cross-sectional view showing a state in which a low
load is applied to the pressure sensitive sensor unit 1A in Fig. 2, and Fig. 3(b)
is a cross-sectional view showing a state in which a high load is applied to the pressure
sensitive sensor unit 1A in Fig. 2.
[0090] As shown in Fig. 3(a), when a low load F
1 is applied to the pressure sensitive sensor unit 1A from the plate member 5 side,
the load is transmitted from the plate member 5 to the first load transmitting members
3A to 3D bonded to the lower surface of the plate member 5. That is, the first load
transmitting members 3A to 3D are pressed in the -Z direction in the diagram by the
lower surface of the plate member 5.
[0091] Then, the second base material 21 is bent downward at the first opening 31 by the
load transmitted from the first load transmitting members 3A to 3D. That is, the first
load transmitting members 3A to 3D concentrate the load on the first pressure sensitive
sensors 2A to 2D. As a result, at the first opening 31 of the spacer 30, the connection
bodies 22A to 22D formed on the lower surface of the second base material 21 are pressed
downward to be electrically connected to the first and second electrode groups 13
and 14 of the first pressure sensitive sensors 2A to 2D.
[0092] On the other hand, since the amount of contraction of the first load transmitting
members 3A to 3D is small, the second load transmitting member 4 is spaced apart from
the plate member 5 and accordingly, the load is not transmitted from the plate member
5 to the second load transmitting member 4. Therefore, the second load transmitting
member 4 does not press the second base material 21, and the connection body 22E is
not pressed downward. That is, the third electrode 13E and the fourth electrode 14E
of the first pressure sensitive sensor 2E are maintained in a state (off state) in
which these are insulated from each other.
[0093] As shown in Fig. 3(b), when a high load F
2 is applied to the pressure sensitive sensor unit 1A from the plate member 5 side,
the plate member 5 is pressed further downward and the first load transmitting members
3A to 3D contract significantly. Therefore, the lower surface of the plate member
5 comes into contact with the second load transmitting member 4. That is, in addition
to the first load transmitting members 3A to 3D, the second load transmitting member
4 is also pressed in the -Z direction in the diagram by the lower surface of the plate
member 5.
[0094] The second base material 21 is bent downward at the second opening 32 by the load
transmitted from the second load transmitting member 4. As a result, at the second
opening 32 of the spacer 30, the connection body 22E is pressed downward to be electrically
connected to the third and fourth electrodes 13E and 14E of the second pressure sensitive
sensor 2E.
[0095] Thus, in the pressure sensitive sensor unit 1A according to the present embodiment,
only the first pressure sensitive sensors 2A to 2D are in the ON state when a low
load is applied, whereas not only the first pressure sensitive sensors 2A to 2D but
also the second pressure sensitive sensor 2E is in the ON state when a high load is
applied.
[0096] In addition, as shown in Figs. 1 and 2, the first load transmitting members 3A to
3D are arranged on the upper surface of the second base material 21 so that the first
load transmitting members 3A to 3D surround the second load transmitting member 4.
That is, since the first pressure sensitive sensors 2A to 2D according to the present
embodiment are arranged around the second pressure sensitive sensor 2E, the first
load transmitting members 3A to 3D are also arranged around the second load transmitting
member 4. Therefore, when a load is applied to the pressure sensitive sensor unit
1A, the load can be transmitted uniformly from the lower surface of the plate member
5 while stably supporting the plate member 5 by the plurality of first load transmitting
members 3A to 3D arranged around the second load transmitting member 4. As a result,
it is possible to detect the load accurately.
[0097] The change in the resistance value output from the pressure sensitive sensor unit
1A as described above will be described with reference to Fig. 4 in addition to Figs.
1, 2, 3(a) and 3(b). Fig. 4 is a graph showing the relationship between the magnitude
F of a load applied to the pressure sensitive sensor unit 1A according to the present
embodiment and the resistance value R output from the pressure sensitive sensor unit
1A. In the graph of Fig. 4, the solid line indicates the combined resistance R
0 of the resistance value R
x1 of the first pressure sensitive sensors 2A to 2D and the resistance value R
1 of the resistive body 16, and the broken line indicates the resistance value R
x2 of the second pressure sensitive sensor 2E. In addition, the dashed line indicates
the resistance value R output from the pressure sensitive sensor unit 1A, and in the
present embodiment, the resistance value R is a resistance value between the first
external terminal portion 122 and the second external terminal portion 172.
[0098] First, as shown in Fig. 2, when there is no load, the electrodes 13A to 13E and 14A
to 14E of all the pressure sensitive sensors 2A to 2E are electrically insulated from
each other, so that all the pressure sensitive sensors 2A to 2E are in the OFF state.
In this case, as shown in Fig. 4, a resistance value R
d of several hundred MΩ is output from the pressure sensitive sensor unit 1A as the
resistance value R.
[0099] Then, as shown in Fig. 3(a), when the low load F
1 equal to or greater than a predetermined level is applied to the pressure sensitive
sensor unit 1A, the first pressure sensitive sensors 2A to 2D are switched to the
ON state. In other words, at the low load F
1 equal to or lower than a predetermined level, the resistance value between the connection
bodies 22A to 22D and the first and second electrodes 13A to 13D and 14A to 14D exceeds
a threshold value, so that the first pressure sensitive sensors 2A to 2D are maintained
in the OFF state. In addition, the second pressure sensitive sensor 2E is maintained
in the OFF state in the low load range.
[0100] At this time, as shown in Fig. 1, the first pressure sensitive sensors 2A to 2D are
electrically connected in parallel to each other, and the resistive body 16 is electrically
connected in series to the second electrode group 14 of the first pressure sensitive
sensors 2A to 2D. Therefore, the resistance value R output from the pressure sensitive
sensor unit 1A is the combined resistance R
0 of the resistance value R
x1 of the first pressure sensitive sensors 2A to 2D and the resistance value R
1 of the resistive body 16.
[0101] In this case, as shown in Fig. 4, as the magnitude of the load increases in the low
load range, the resistance value R
x1 of the first pressure sensitive sensors 2A to 2D decreases, and finally the resistance
value R
x1 saturates at the minimum resistance value (push-through resistance) R
min. For this reason, as shown by the solid line in the graph of Fig. 4, the combined
resistance R
0 also decreases as the magnitude of the load increases, and finally saturates near
the resistance value R
min + R
1.
[0102] Then, as shown in Fig. 3(b), when the high load F
2 is applied to the pressure sensitive sensor unit 1A, the second pressure sensitive
sensor 2E is also switched to the ON state. As shown by the broken line in the graph
of Fig. 4, as the magnitude of the load increases in the high load range, the resistance
value R
x2 of the second pressure sensitive sensor 2E decreases. Since no resistive body is
connected to the second pressure sensitive sensor 2E and the resistance value R
1 of the resistive body 16 described above is larger than the resistance value R
x2, the resistance value R
x2 falls below the value of the combined resistance R
0 when the magnitude of the high load reaches a magnitude equal to or greater than
a predetermined level.
[0103] When the resistance value R
x2 falls below the value of the combined resistance R
0 described above, the current flowing through the second pressure sensitive sensor
2E becomes more dominant than the current flowing through the first pressure sensitive
sensors 2A to 2D. Therefore, the resistance value R output from the pressure sensitive
sensor unit 1A becomes the resistance value R
x2 of the second pressure sensitive sensor 2E. Thus, in the present embodiment, by electrically
connecting the resistive body 16 in series to the second electrode group 14, the range
of the resistance value output in the low load range and the range of the resistance
value output in the high load range can be distinguished from each other to avoid
duplication.
[0104] Then, since the resistance value R
x2 of the second pressure sensitive sensor 2E saturates near the push-through resistance
value R
min as the magnitude of the load further increases, the resistance value R output from
the pressure sensitive sensor unit 1A also saturates near the push-through resistance
value R
min. Therefore, the resistance value R of the pressure sensitive sensor unit 1A becomes
an output shown by the dashed line in Fig. 4.
[0105] The pressure sensitive sensor unit 1A described above includes the first load transmitting
member 3A to 3D for transmitting a low load to the first pressure sensitive sensor
2A to 2D and the second load transmitting member 4 for transmitting a high load to
the second pressure sensitive sensor 2E. Therefore, since the pressure sensitive sensor
unit 1A can obtain an output (resistance value R) in both the low load range and the
high load range, it is possible to increase the detectable load range.
[0106] In addition, in the embodiment described above, the first load transmitting members
3A to 3D, the second load transmitting member 4, and the plate member 5 are arranged
on the second base material 21 side of the upper membrane substrate 20, but the invention
is not limited thereto.
[0107] Fig. 5 is a cross-sectional view showing a first modification example of the pressure
sensitive sensor unit according to the present embodiment. Like a pressure sensitive
sensor unit 1B according to the first modification example, the first load transmitting
members 3A to 3D, the second load transmitting member 4, and the plate member 5 may
be arranged on the first base material 11 side of the lower membrane substrate 10.
[0108] In this case, when a low load is applied from the second base material 21 side, the
load is transmitted to the first pressure sensitive sensors 2A to 2B by the first
load transmitting members 3A to 3D, as in the embodiment described above. Then, when
a high load is applied from the second base material 21 side, as in the embodiment
described above, as the first load transmitting members 3A to 3D contract, the second
load transmitting member 4 comes into contact with the plate member 5 and accordingly,
the load is transmitted to the first pressure sensitive sensors 2A to 2B. In addition,
in this case, it is preferable to make the second base material 21 difficult to bend.
Specifically, two or more second base materials 21 may be stacked on the spacer 30,
or the thickness of the second base material 21 may be increased. In addition, as
the first base material 11 to which the load is transmitted from the first and second
load transmitting members 3A to 3D and 4, a flexible one is used.
[0109] In addition, in the embodiment described above, the height T
1 of the first load transmitting members 3A to 3D is set to be higher than the height
T
2 of the second load transmitting member 4 so that a load is less likely to be applied
to the second pressure sensitive sensor 2E in the low load range, but the invention
is not limited thereto.
[0110] Fig. 6 is a cross-sectional view showing a second modification example of the pressure
sensitive sensor unit according to the present embodiment. As in a pressure sensitive
sensor unit 1C according to the second modification example, a second load transmitting
member 4b may be made softer than the first load transmitting members 3A to 3D so
that a load is less likely to be applied to the second pressure sensitive sensor 2E
in the low load range. As a material that makes up the second load transmitting member
4b, a material having a low Young's modulus among the above-described sponge-like
resin material, rubber material, and spring material may be used.
[0111] In addition, in this case, the height T
1 of the first load transmitting members 3A to 3D and the height T
2 of the second load transmitting member 4b are the same (T
1 = T
2). Since the first load transmitting members 3A to 3D are harder than the second load
transmitting member 4b, a load is more easily transmitted to the first load transmitting
members 3A to 3D than to the second load transmitting member 4b in the low load range.
Therefore, in the second modification example as well, similarly to the embodiment
described above, a load is less likely to be applied to the second pressure sensitive
sensor 2E in the low load range.
[0112] In addition, in the embodiment described above, interdigitated comb-shaped electrodes
are used as the first and second electrodes 13A to 13E and 14A to 14E of the first
pressure sensitive sensors 2A to 2E, but the shape of each electrode is not limited
thereto. The shape of each electrode may be a shape shown in the following third modification
example.
[0113] Fig. 7(a) is an enlarged plan view showing a pressure sensitive sensor according
to the third modification example of the pressure sensitive sensor unit according
to the embodiment of the invention, Fig. 7(b) is an enlarged plan view showing a lower
membrane of the pressure sensitive sensor in Fig. 7(a), and Fig. 7(c) is an enlarged
plan view showing an upper membrane of the pressure sensitive sensor in Fig. 7(a).
[0114] As shown in Figs. 7(a) and 7(b), a first pressure sensitive sensor 2d of a pressure
sensitive sensor unit 1D according to the third modification example is a pressure
sensitive sensor in which a resistance value between wiring patterns 62 and 66 changes
according to the applied load. A first electrode 13d in the third modification example
has wiring patterns 62 and 63, a resistive body 64, and comb-tooth patterns 65A to
65F.
[0115] As shown in Fig. 7(b), the wiring patterns 62 and 63 are formed by printing the low-resistance
conductive paste described above on the upper surface of the first base material 11
of the lower membrane substrate 10d and solidifying (curing) the conductive paste.
In addition, instead of using the conductive paste, the wiring patterns 62 and 63
may be formed by etching a metal foil.
[0116] As shown in Fig. 7(b), the wiring pattern 62 extends linearly along the X direction
in the diagram. An end portion 621 of the wiring pattern 62 is covered with the resistive
body 64, and the comb-tooth pattern 65A is connected to the end portion 621. Similarly,
the wiring pattern 63 also extends linearly along the X direction in the diagram.
An end portion 631 of the wiring pattern 63 is covered with the resistive body 64,
and the comb-tooth pattern 65F is connected to the end portion 631. Although not particularly
shown, one wiring pattern 62 is connected to a power supply, whereas the other wiring
pattern 63 is connected to the ground. In addition, the planar shapes of the wiring
patterns 62 and 63 are not limited to the linear shapes described above so long as
these are linear.
[0117] The end portion 621 of the wiring pattern 62 and the end portion 631 of the wiring
pattern 63 are arranged so as to be spaced apart from each other in the Y direction
in the diagram. The resistive body 64 is provided along the Y direction in the diagram,
so that one end portion 641 of the resistive body 64 covers the end portion 621 of
the wiring pattern 62 and the other end portion 642 of the resistive body 64 covers
the end portion 631 of the wiring pattern 63. Therefore, the wiring pattern 62 on
one side and the wiring pattern 63 on the other side are electrically connected to
each other through the resistive body 64. The resistive body 64 is formed by printing
a high-resistance conductive paste on the upper surface of the base material 11 and
then curing the conductive paste.
[0118] The plurality of (six in this example) comb-tooth patterns 65A to 65F are formed
by printing a low-resistance conductive paste on the first base material 11 and curing
the conductive paste, similarly to the wiring patterns 62 and 63 described above.
In addition, instead of using the conductive paste, the comb-tooth patterns 65A to
65F may be formed by etching a metal foil.
[0119] The comb-tooth patterns 65A to 65F are arranged substantially parallel to each other
at distances therebetween in a facing region 611 of the first base material 11 facing
the connection body 22A. The comb-tooth patterns 65A to 65F are aligned at distances
therebetween from the inside to the outside in the facing region 611. In addition,
the comb-tooth patterns 65A to 65F are arranged concentrically with respect to the
center CP of a distal end portion 661 of the wiring pattern 66 in the facing region
611.
[0120] A second electrode 14d in the third modification example is the wiring pattern 66.
The wiring pattern 66 is also formed by printing a low-resistance conductive paste
on the upper surface of the base material 11 and then curing the conductive paste,
similarly to the wiring patterns 62 and 63 described above. In addition, instead of
using the conductive paste, the wiring pattern 66 may be formed by etching a metal
foil.
[0121] As shown in Fig. 7(c), the configuration of the connection body 20A formed on the
lower surface of the second base material 21 of the upper membrane substrate 20d is
the same as that in the embodiment described above.
[0122] In the first pressure sensitive sensor 2d, when a load is applied, first, the connection
body 22A comes into contact with the center CP of the distal end portion 661 of the
wiring pattern 66 shown in Fig. 7(b). Then, as bending at the first opening 31 of
the second base material 21 increases, the connection body 22A comes into contact
with the comb-tooth pattern 65F.
[0123] When the connection body 22A is in contact with the wiring pattern 66 and the comb-tooth
pattern 65F, the wiring pattern 66 detects a voltage that is almost the same potential
as the ground, and a potential difference between the power supply voltage and the
detected voltage of the wiring pattern 66 is output from a multimeter (not shown)
or the like connected to the wiring patterns 62 and 66.
[0124] Then, as the applied load increases, the bending of the second base material 21 increases,
and the connection target of the connection body 22A expands to the outer comb-tooth
patterns 65E to 65A. Therefore, the distance between one end portion 641 of the resistive
body 64 and the connection position of the connection target decreases, resulting
in a decrease in the resistance value between the wiring patterns 62 and 66. That
is, in the first pressure sensitive sensor 2d according to the third modification
example, since the resistance length (resistance value) of the resistive body 64 changes
according to the magnitude of the applied load, the voltage detected by the wiring
pattern 66 changes according to the magnitude of the load.
[0125] In the third modification example, an example has been described in which the first
pressure sensitive sensor 2d has the configuration shown in Fig. 7(a). However, the
invention is not limited thereto, and the second pressure sensitive sensor may also
have the configuration as shown in Fig. 7(a).
[0126] In addition, although not particularly shown, the wiring pattern 63 may not be provided
and the power supply and the ground may be connected to the wiring patterns 62 and
66. Alternatively, instead of the wiring pattern 63, the wiring pattern 66 may be
covered with the other end portion 642 of the resistive body 64. Even in these cases,
the resistance value between the wiring patterns 62 and 66 changes according to the
magnitude of the load.
[0127] In addition, in the embodiment described above, a case has been described in which
all of the first to fourth electrodes are formed on the same base material and the
first to fourth electrodes are electrically connected to each other by the connection
body, but the invention is not limited thereto. As in the following fourth modification
example, electrodes may be electrically connected to each other by direct contact
between the electrodes.
[0128] Fig. 8(a) is an enlarged cross-sectional view showing a pressure sensitive sensor
according to a fourth modification example of the pressure sensitive sensor unit according
to the present embodiment, Fig. 8(b) is an enlarged plan view showing a lower membrane
of the pressure sensitive sensor in Fig. 8(a), and Fig. 8(c) is an enlarged plan view
showing an upper membrane of the pressure sensitive sensor in Fig. 8(a).
[0129] As shown in Figs. 8(a) to 8(c), a first pressure sensitive sensor 2e of a pressure
sensitive sensor unit 1E according to the fourth modification example includes a disk-shaped
first electrode 13e formed on the upper surface of a first base material 11 of a lower
membrane substrate 10e and a disk-shaped second electrode 14e formed on the lower
surface of a second base material 21 of an upper membrane substrate 20e.
[0130] The first electrode 13e and the second electrode 14e face each other at the first
opening 31 of the spacer 30. The first and second electrodes 13e and 14e can be formed
by printing and curing a pressure sensitive ink, for example. An example of the pressure
sensitive ink is a quantum tunnel composite material using the quantum tunneling effect.
In addition, other specific examples of the pressure sensitive ink include one containing
conductive particles such as metal or carbon, elastic particles such as organic elastic
filler or inorganic oxide filler, and a binder. The surface of the pressure sensitive
ink is made uneven by the elastic particles. In addition, the first and second electrodes
13e and 14e may be formed by plating or patterning.
[0131] When a load is applied to the first pressure sensitive sensor 2e, the second base
material 21 bends downward at the first opening 31, causing the first electrode 13e
and the second electrode 14e to come into contact with each other and become electrically
connected to each other.
[0132] In the fourth modification example, an example has been described in which the first
pressure sensitive sensor 2e has the configuration shown in Fig. 8(a). However, the
invention is not limited thereto, and the second pressure sensitive sensor may also
have the configuration shown in Fig. 8(a).
[0133] In addition, the embodiment described above is described to facilitate the understanding
of the invention, and is not described to limit the invention. Therefore, each element
disclosed in the above-described embodiment is intended to include all design changes
or equivalents falling within the technical scope of the invention.
EXPLANATIONS OF LETTERS OR NUMERALS
[0134]
1A to 1E PRESSURE SENSITIVE SENSOR UNITS
2 PRESSURE SENSITIVE SENSOR SHEET
2A to 2D, 2d, 2e FIRST PRESSURE SENSITIVE SENSORS
2E SECOND PRESSURE SENSITIVE SENSOR
10, 10d, 10e LOWER MEMBRANE SUBSTRATES
11 BASE MATERIAL
12 FIRST WIRING PATTERN
121a, 121b FIRST AND SECOND WIRING PORTIONS
122 FIRST EXTERNAL TERMINAL PORTION
13 FIRST ELECTRODE GROUP
13A to 13D, 13d, 13e FIRST ELECTRODES
14 SECOND ELECTRODE GROUP
14A to 14D, 14d, 14e SECOND ELECTRODES
13E THIRD ELECTRODE
14E FOURTH ELECTRODE
131, 141 CONNECTION WIRING PORTION
132, 142 COMB-TOOTH PORTION
135A to 135D FIRST DETECTION UNITS
135E SECOND DETECTION UNIT
15 SECOND WIRING PATTERN
151 THIRD WIRING PORTION
153 FIRST RESISTIVE BODY CONNECTION PORTION
16 RESISTIVE BODY
17 THIRD WIRING PATTERN
171a, 171b FOURTH AND FIFTH WIRING PORTIONS
172 SECOND EXTERNAL TERMINAL PORTION
173 SECOND RESISTIVE BODY CONNECTION PORTION
62 WIRING PATTERN
621 END PORTION
63 WIRING PATTERN
631 END PORTION
64 RESISTIVE BODY
641, , 642 END PORTION
65A to 65F COMB-TOOTH PATTERNS
655 DETECTION UNIT
66 WIRING PATTERN
661 DISTAL END PORTION
20, 20e UPPER MEMBRANE SUBSTRATE
21 BASE MATERIAL
22A to 22E CONNECTION BODIES
30 SPACER
31 FIRST OPENING
32 SECOND OPENING
3A to 3D FIRST LOAD TRANSMITTING MEMBERS
4, 4b SECOND LOAD TRANSMITTING MEMBER
5 PLATE MEMBER